Electroplated and/or electroformed iron is known to have superior ferromagnetic properties. For example, a 0.0001 inch thick by 1.0 square inch deposit on a 0.5 inch non-ferro-magnetic stainless steel shaft which is 12 inches long enables the shaft to be picked up with a magnet. This superior ferro-magnetic property is possible with iron prepared by an electrolytic process because this method is capable of producing iron of very high purity. Yet, while methods of electrodepositing iron are known, an efficient method for continuously electrodepositing iron on a commerical scale is not known, primarily because of the instability of the electrolyte solution used in the process. Much effort has been devoted without success to a search for stable electrolytes for the process. There is a need for a method of electrodepositing iron wherein a stable electrolyte solution can be maintained throughout the process.
U.S. Pat. No. 4,231,847 to Lui discloses a method for electrodepositing nickel-iron alloys. In this method, an electrolyte solution containing nickel chloride and ferrous sulfate is used to deposit nickel and iron onto a substrate in specified proportions. The pH of the Lui electrolyte solution is stated to be critical, being maintained at less than 3 and preferably from 1 to 3. Free oxygen is excluded from the electrolyte solution, and the solution is agitated during deposition, by bubbling inert gas through the electrolyte solution while current is passed through the electrolyte solution thereby depositing the iron-nickel alloy onto the substrate. Such a process has significant drawbacks. Bubbling the inert gas through the electrolyte solution during electrodeposition requires plating at lower current densities such as 30-50 amps per square foot. Deposition speed is thus quite low. The bubbling also would result in substantial evaporation of electrolyte solution components such as water and hydrogen chloride (used by Lui as a pH adjuster). This results in difficult-to-predict electrolyte solution compositions and concentrations and pH variations during the process, as well as requiring substantial efforts to dispose of or recycle the resulting waste gas and vapor. The bubbling would also cause marks on the outer surface of the electrodeposited material and would cause difficulties with foaming and temperature control.
U.S. Pat. No. 4,414,064 to Stachurski et al. discloses a method for preparing low voltage hydrogen cathodes wherein the cathode comprises an active surface portion from a codeposit of three metals, including iron. Certain conductive metals or alloys, including a titanium-palladium alloy containing 0.2% palladium, are disclosed to be suitable materials for the substrate, having the required electrical and mechanical properties for use as a cathode, and chemical resistance to the particular electrolytic solution. In chlorate cells, where corrosion of the substrate material may be a problem, titanium or titanium alloys are said to be preferred.
U.S. Pat. No. 4,664,758 to Grey discloses an electroforming process comprising: 1) providing an elongated electroforming mandrel core; 2) applying a substantially uniform coating of a molten, inert, inorganic, homogeneous, electrically conductive metal or metal alloy to the mandrel core, the metal or metal alloy having a melting point and surface tension less than that of the mandrel core; 3) immersing the mandrel core bearing the coating in an electroforming bath; and 4) removing the electroformed metal from the mandrel core. Suitable metals capable of being deposited by electroforming are said to include iron; suitable mandrel cores are said to include titanium-palladium alloys.
U.S. Pat. No. 4,400,408 to Asano et al. discloses a method for forming an anticorrosive coating on the surface of a metal substrate. Suitable metal substrates are said to include titanium alloys and iron. Metals suitable for coating on the surface of the substrate are said to be those which have excellent corrosion resistance and which can be alloyed with the substrate metal.